Conventionally, an operating area of an industrial robot is enclosed by a safety fence, and the safety fence separates a worker from the industrial robot. In recent years, because of an improvement of industrial robots in control capabilities, sharing of the workspace between the worker and the industrial robot is able to be theoretically realized. However, if the industrial robot is enclosed by the safety fence, the worker cannot easily access to the interference area.
On the other hand, without providing the conventional safety fence, a system which avoids interference between the industrial robot and the worker is proposed by monitoring that the worker and objects enter into an area around the industrial robot. For example, a system disclosed in Patent Document 1 includes a sensor part which monitors an entry of an unregistered new object into an operating area of a robot, a visible light irradiating part which irradiates visible light to a perimeter part of the operating area from a position higher than the robot, and a monitoring controller which issues a stop demand to the robot when the sensor part determines that there is an entry of the new object into the operating area. The irradiation of visible light may be performed only when there is an entry of the new object into a surveillance area which includes the operating area. In this system, a situation where the worker enters into the operating area to stop the robot is reduced without installing the safety fence around the robot, by attracting the worker's attention to the robot operating area with the visible light.